In June, a panel of square-shouldered military chiefs sat before Congress to account for the epidemic of sexual assault. Top brass promised “zero tolerance,” and Congress began crafting reforms tied to the defense spending bill it will send to the White House this year.

Everyone says they are committed to reform—the Pentagon has been promising change for decades—but since the June hearing most lawmakers have backed away from one check that victims’ advocates argue is crucial and the military says is out of the question: authorizing military lawyers, rather than commanding officers, to decide which cases go to trial.

That policy has been adopted by peer militaries including Germany and the United Kingdom, but in Congress it has opened a fault between Senate Democrats. Toeing the Pentagon line, Armed Services Committee heavyweights Carl Levin and Claire McCaskill are fighting to put down Kirstin Gillibrand’s measure granting military prosecutors authority in serious criminal cases, thus taking the chain of command out of the legal process.

As it stands now victims must report crimes against them to their commanding officer, who then decides whether the complaint warrants a trial. Victims’ advocates argue that lawyers, not officers, should determine a case’s legality, and that preserving the command structure leaves victims vulnerable to retaliation and conflicts of interest, discouraging them from reporting crimes.

The Armed Services Committee, led by Levin, killed Gillibrand’s corrective after she introduced it as an amendment to the Defense Authorization Act and instead passed a softer measure that upholds commanding officers’ convening authority. Since then Gillibrand has been trying to drum up a bipartisan coalition strong enough to reintroduce her amendment when the defense spending bill comes to the Senate floor as soon as next week. She needs fifty-one co-sponsors to open discussion, and so far has thirty-four, including Republicans Charles Grassley, Lisa Murkowski, Susan Collins and Mike Johanns.

Tea Party darlings Ted Cruz and Rand Paul gave Gillibrand an unlikely boost on Tuesday when they announced they were signing onto her amendment. “There can be no prosecution and no deterrent if we don’t have reporting of the crimes,” said Cruz at a news conference. Their support hinged on the clarification that commanding officers would retain jurisdiction over crimes of a uniquely military nature, such as disobeying orders or going absent without leave. “I see no reason why conservatives shouldn’t support this,” Paul added. “The only thing I think is standing in the way is just sort of the status quo.”

Pentagon policy is a hard-shell status quo, and where the chain of command is concerned, Levin and McCaskill are keen to preserve it. They argue that Congress is enforcing other measures to overhaul the system, and that removing the chain of command would in fact lower the rate of prosecution. That point emerged Thursday during a re-confirmation hearing for Joint Chiefs of Staff chairman general Martin Dempsey and vice chairman staff admiral James Winnefeld, who testified that commanders have pursued cases that civilian prosecutors declined, and won convictions.

“If outside prosecutors are making the decisions, the chance of retaliation goes up, not down,” McCaskill told The Nation after the hearing. “If everybody in the unit knows the commander has said ‘this needs to go to court,’ that gives you a level of protection you will never have when everyone knows a bunch of outside lawyers have bought your bull.”

According to Winnefeld’s testimony, the Army found forty-nine cases in the last two years in which civilian lawyers declined to prosecute; commanders pursued the cases, leading to twenty-five convictions. The Marine Corps reported twenty-eight cases declined by prosecutors that commanders pursued to sixteen convictions. To McCaskill and Levin, this data indicates that empowering prosecutors would lead to fewer convictions.

But the role of civilian prosecutors in criminal court is not comparable with military lawyers, who are not elected and work within the military legal system. It’s good that commanders added forty-one convictions, but that number vanishes into the gap between the 302 convictions won in 2012 and the 2,558 pursued.

And of the cases pursued by commanders that Winnifeld pointed out, “we don’t know if those are cases that the civilians had written off, or—more likely—that the military requested jurisdiction and civilians agreed to give it to them,” said Brian Purchia of the victims’ advocacy group Protect Our Defenders. “It doesn’t change the fact that rapes and sexual assaults are increasing while reporting and convictions are down.”

McCaskill maintained that the Senate is “making changes that will really impact the success of these cases” by reforming what happens “the moment the victim reports,” measures which include making retaliation a crime and requiring a senior officer to review all cases in which a commander declines to prosecute a sexual assault against the recommendation of his lawyers. Such instances are rare.

What happens after a victim reports is critical, but few get that far. Only about 3,300 victims came forward in 2012, while an estimated 26,000 instances of “unwanted sexual contact” occurred. “We’re still having 23,000 victims who don’t feel the system is strong enough, objective enough, and transparent enough to even report,” Gillibrand said at the hearing.

McCaskill, a former prosecutor, expressed a lot of faith that the system will fix itself. “We have made massive changes in a relatively short period of time, and without giving them a chance to work. There’s a little bit of a political rush to judgment now,” she said. “There is this notion that this one other piece is the magic elixir that will all of a sudden make the military be perfect when it comes to sexual assault, and it’s naïve and I think frankly comes from not having as much experience as some of us have in this particular arena.”

Taryn Meeks, a former Navy lawyer (judge advocate general, or JAG, in military terms) now the executive director of Protect Our Defenders, disagreed with McCaskill’s assessment. “The public eye is on commanders now, but what happens when the public shifts its attention? The system is so broken it will easily revert back to a time when commanders can sweep these issues under the rug,” she said.

McCaskill is playing defense after a Politico story alleged that the amendment she and Levin pushed over Gillibrand’s was vetted first by the Pentagon, a claim McCaskill denies. “I resent being characterized as a tool of the Pentagon on this,” she said after the hearing, during which she pounded her fist on the table and told Dempsey and Winnefeld, “There is nobody who will be further in front of the line to kick you until you’re senseless if we don’t get this problem under control.”

But her support for preserving commanders’ convening authority doesn’t add up, particularly since she’s been so vocal about the urgency of the sexual assault crisis. McCaskill has argued that keeping prosecution within the chain is the only way to ensure that commanders are fully invested in stamping out sexual violence; that’s hardly a vote of confidence for the commitment they say is absolute. As Meeks pointed out, giving trained military lawyers authority over serious crimes “is not going to undermine commanders’ responsibility to have a healthy command climate.”

The fundamental question the debate raises is whether Congress retains the ability to enforce civilian control over the military. If Gillibrand rouses fifty-one co-sponsors, the floor debate will likely be heated. The House, which passed its defense bill last month with added protections for victims, harsher sentencing for perpetrators and no change to convening authority, would give the amendment a tougher reception. Some reform to the military’s justice system will pass, but whether it will be an effective overhaul or a half-measure remains to be seen.

“If five years from now we’re having fewer sexual assault convictions, if we have fewer reports of sexual assault that appear to be an anomaly in terms of the overall incidents coming down, I’ll be first in line,” McCaskill told The Nation. “I’m going to get this fixed.”

With 23,000 unreported cases a year, waiting to see if the Pentagon is as good as its word is a high stakes gamble.